Method and apparatus for simultaneously fractionating a plurality of crude oils

ABSTRACT

1. A FRACTIONATING TOWER FOR SEPARATING AT LEAST TWO DIFFERENT CRUDE OIL CHARGE MATERIALS SIMULTANEOUSLY COMPRISING IN COMBINATION: A CYLINDRICAL DISTILLATION CHAMBER SEPARATE FROM A PLURALITY OF ADJACENT SEPARATE DISTILLATION CARTRIDGE MEANS POSITIONED IN THE LOWER PORTION OF THE TOWER, AN ELONGATED REDTIFICATION SECTION ABOVE SAID DISTALLATION MEANS AND CONTAINING A PLURALITY OF VERTICALLY SPACED APART FRACTIONATING TRAYS, EACH OF SAID DISTILLATION MEANS PROVIDED WITH A PLURALITY OF VERTICALLY SPACED APART DISTILLATION TRAYS, THE UPPER END OF EACH OF SAID DISTILLATION MEANS BEING IN OPEN COMUNICATION WITH THE BOTTOM PORTION OF SAID RECTIFICATION CHAMBER AND SEPARATE THEREFROM BY TRAY MEANS ARRANGED TO CHANNELL LIQUID COLLECTED THEREON INTO SAID CARTRIDGE DISTILLATION MEANS, FEED INLET MEANS TO AN UPPER INNER FLASH ZONE PORTION OF SAID CYLINDRICAL DISTILLATION CHAMBER AND FEED INLET MEANS TO AN ANNULAR SECTION F SAID TOWER ABOVE SAID CARTRIDGE DISTILLATION MEANS, SPACED APART LIQUID WITHDRAWAL AND INLET MEAND THROUGHOUT THE VERTICAL HEIGHT OF SAID RECTIFICATION SECTION, AND MEANS FOR WITHDRAWING RESIDUAL PRODUCT FROM THE BOTTOM OF SAID CYLINDRICAL DISTILLATION CHAMBER SEPARATELY FROM THE BOTTOM OF SAID ANNULAR SECTION.

1974 H. B. MERRIMAN .8 55

METHOD AND APPARATUS FOR smuurmnousm FRACTIONATIHG A PLURALITY or CRUDE OILS Filed Nov. 16, 1973 2 Sheets-Sheet 1 FIGURE 1 1974 H. B. MERRIMAN 3. 56

METHOD AND APPARATUS FOR SIMULTANEOUSLY FRACTIONATING A PLURALITY OF CRUDE OILS Filed Nov. 16, 1973 2 Sheets-Sheet 2 FIGURE 2 :0 I |-||-.I i-ll l I T Q 0' F |GURE4 24 FIGURE 5 United States Patent O 3,846,249 METHOD AND APPARATUS FOR SIMULTANE- OUSLY FRACTIONATING A PLURALITY F CRUDE OILS Horace B. Merriman, South Ascot, England, assignor to Mobil Oil Corporation Filed Nov. 16, 1973, Ser. No. 416,423 Claims priority, application Great Britain, Nov. 30, 1972, 55,292/ 72 Int. Cl. B0111 3/30 US. Cl. 196-111 Claims ABSTRACT OF THE DISCLOSURE A crude fractionating tower design is described which provides for processing two different crude oil charge materials to produce at least two separate residual compositions which may be separately withdrawn from a lower portion of the tower. The fractionating tower is provided with a common upper refluxing section above a concentric cylindrical stripping-distillation section circumscribed in an annular section of the vessel by a plurality of separate satellite stripping-distillation cartridges positioned between the concentric cylindrical section and the tower wall.

BACKGROUND OF THE INVENTION It has been a common practice with petroleum refiners to take advantage of various crude oil sources by blending the crudes and fractionating the same to obtain a plurality of liquid fractions including gasoline, kerosine, light gas oil, heavy .gas oils and a residuum. Thus with crudes including sulfur, substantial portions of the heavier components of the crude blend become concentrated in the residuum rather than in other liquid fractions. As is known, a high sulfur residuum is considered a poor quality fuel and thus of relatively low market value. On the other hand, low sulfur residuums are considered to be relatively high quality fuel and bring a better price. Therefore, when blending high sulfur crudes with low sulfur crudes an economic disadvantage is presented by down-cutting the initially low sulfur crude. An alternative procedure for processing crudes of such different characteristics has been the reliance upon separate fractionation of each. This procedure, however, is exceedingly expensive due to the numerous storage tanks required with associate piping and other equipment to store the crudes as well as the products obtained therefrom including a separate storage of low and high sulfur residuums. The present invention is concerned with solving many of these prior art problems by providing apparatus for the concurrent distillation and/or fractionation of petroleum crudes differing considerably in composition or at least differing in the amount of sulfur therein so that compatible common distillate fractions may be obtained therefrom as well as high and low sulfur residuum from each of the crudes.

SUMMARY OF THE INVENTION The present invention is concerned with the design and method of operation of a crude fractionating tower provided with a plurality of separate distillation sections in the lower portion thereof provided in part by a concentric cylindrically shaped distillation section of smaller diameter than said fractionating tower thereby forming an annular section containing separate distillation cartridges. The tower is provided with a common refluxing or rectification section above the concentric cylindrical bafiie member. The lowermost tray of the rectification section is arranged to discharge liquid collected thereon into the annulus of the tower formed by the concentric baffie member. The fractionating tower of this invention is designed for handling two separate crude charge materials such as 3,846,249 Patented Nov. 5, 1974 low and high sulfur crude oils so that residual products thereof may be separately recovered from a bottom portion of the tower without fear of contamination of one by the other.

In yet another aspect the present invention relates to the method for the concurrent distillation and fractionation of petroleum crudes differing in composition to obtain separate residues thereof as well as a plurality of common distillate fractions from each of the charged crude material.

The fractionating tower design of the present invention departs from and is an improvement over the prior art in several respects. That is, in the tower arrangement of this invention a concentric cylindrical baflie member providing an inner stripping-distillation section is substantially operationally independent as it should be for handling a different hydrocarbon charge in an annular section thereabout. Thermal stresses caused by processing different hydrocarbon fluids at different temperatures in at least the lower portion of the tower comprising the distillation section is also more safely accommodated by the concentric cylindrical baffle arrangement and therefore restrictions on processing temperature limits placed on either hydrocarbon stream introduced to the tower can be very general. The tower design also minimizes construction material for its fabrication and particularly the welding requirements thereof for sealing the separate distillation sections. Welding of components within the tower during fabrication can also be considerably minimized by prefabrication of relatively large components thereof externally to the tower. A further important advantage in the tower design of this invention resides in keeping the fractionation tray assemblies simple and at the same time of the most suitable configuration for processing considerations. It will be observed that the hour glass configuration of the central concentric cylindrical chamber permits grouping the annular tray area into four simplified satellite distillation cartridges which are housed within the annulus provided in the lower portion of the tower.

From the above it is clear that a considerably improved design is provided for processing two different hydrocarbon charge materials in a single fractionator tower configuration.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic representation in elevation of a fractionating tower provided With a concentric generally cylindrical distillation section in the lower portion thereof surrounded by a plurality of separate satellite distillation cartridges.

FIG. 2 is a diagrammatic representation of the crosssection AA of the fractionating tower of FIG. 1 showing steam inlet conduits P1, P2 and P3.

FIG. 3 is a diagrammatic representation of the crosssection Y--Y of the fractionating tower of FIG. 1.

FIG. 4 is a diagrammatic representation of the tangential feed inlet of the concentric cylindrical distillation section of the fractionating tower of FIG. 1.

DESCRIPTION OF THE SPECIFIC EMBODIMENT The crude fractionating tower of FIG. 1 is designed for the purpose of separating two different crude charge streams varying in composition into common products of distillation and separate residua products of each crude stream charged. In a specific application a first crude stream identified as Arabian Light Crude in Table 1 below is introduced by conduit N1 for initial distillation within the concentric cylindrical baffie section and a second crude charge stream identified as Kuwait Crude in Table 1 below is introduced by conduit N2 to the annular section of the distillation tower. Products of atmospheric distillation of each crude are provided in Table 2 below.

TABLE 1 Crude Crude Arabian Kuwait light Gravity, API 31.4 34. 5 B.P.S.D 60, 000 90, 000 Weight percent sulfur. 2. 5 1. 65

Kuwait-Arabian light distillates Gravity, B P.S.D

AII product Unstabilized naphtha 79. 5 23, 680 Heavy naphtha 57. 8,860 Light kerosine. 48. 9 13, 500 Heavy kerosine. 42. 6 12, 970 Gas oil 3-5. 8 21, 360

Arabian Kuwait light resid. resid Gravity, API 12. 7 18. 9 .P.S. 28,000 41,550 Sulfur, weight percent 3. 95 2.87 Viscosity, cs. at 210 F- 56 16 Pour, F 66 45 Overhead gasiform material is removed fromthe upper portion of the tower, passed through a cooler and then to a knock-out drum, not shown. A portion of this cooled overhead is withdrawn and returned to the tower as reflux material as known in the prior art. During operation of the crude tower, common distillation product streams are removed, as identified in Table 3. The common distillation fractions withdrawn are passed to separate adjacent stripping zones as known in the art but not shown. An overhead vaporous material obtained from each of the adjacent stripping zones is returned separately to the crude tower as identified by Table 3. It is to be understood of course that the conditions for operating the tower of FIG. 1 may be varied considerably depending on the crude materials charged thereto and products desired therefrom.

Referring now to FIG. 1 by way of example, there is shown diagrammatically in elevation the tower design of the present invention and particularly the design improvement thereof concerned with locating a concentric cylindrical distillation section identified by baffle 6 within the lower portion of tower 2 and surrounded by a plurality of separate satellite distillation cartridges 4. Table 3 above identifies the various inlet and withdrawal means TABLE 2.CRUDE DISTILLATION PRODUCTS Arabian Kuwai S.R. Light Heavy Atmos. atmos. atmos.

gasoline Naphtha kerosine kerosine gas oil resid. resid.

ASTM. 1.13.1. F.) 234 320 347 412 478 244 340 403 482 590 250 349 414 511 621 20%-. 255 356 439 540 628 261 361 450 556 360 268 370 468 585 277 383 482 612 S0% 282 392 495 628 291 408 509 651 208 419 523 669 F B 246 338 439 554 700 .P Flash point, PMCCW F Pour p0int, F

1 Cracked, 24% recovered.

2 Cracked at 31%.

3 Pensky Martins Closed Cup.

In a specific application the atmospheric crude tower of FIG. 1 is operated with a bottom pressure of about 30 p.s.i.g. employing a crude charge temperature thereto of about 660 F. Residua product of each crude charged is Withdrawn from the bottom of the tower as separate streams at a temperature of about 630 F. Numerous side streams are introduced and withdrawn as identified by the following Table 3.

of the tower of FIG. 1. It is to be noted that segmented portions of the tower not going to the essence of the invention have been eliminated to reduce the overall height of the drawing. For example, near the top of the tower, trays 28 and 29 have been deleted leaving the uppermost tray 30. Also trays 26, 21, 14 and 15 have been deleted. In the distillation section a portion of the flash zone has been deleted as well as a portion of the residua collection section in the bottom of the tower. In FIG. 1, the upper portion of the tower and particularly that portion shown above tray 5 which is a bubble cap tray immediately above the open upper end of concentric baffle 6 is known as the rectification section of the fractionating tower. The rectification section is provided with vertically spaced apart sieve or valve trays in an arrangement similar to that depicted in the drawing. A specific showing is made, however, with respect to several trays provided with liquid collection means from which liquid is withdrawn by suitable withdrawal means. Tray 5 being the lowermost tray of the rectification section of tower 2 is preferably a bubble cap tray as shown on the drawing but other types may be employed. Tray 5 is provided with downcomer and liquid collecting means as shown. Liquid collected on tray 5 is also caused to flow into the annual section of the tower housing a plurality of satellite distillation cartridges more fully discussed below.

Within the lower portion of the tower beneath tray 5 there is provided a generally cylindrical concentric baffle means 6 of larger diameter in the upper portion than in the lower cylindrical portion thereof identified as cylindrical section 8 with an intermediate cylindrical section 10 connected by frusto-conical batfie means 12 and 14. A plurality of distillation trays 16 are located within the concentric cylindrical section of intermediate diameter. The distillation trays within cylindrical section are provided with alternating downcomers arranged for directing the flow of liquid across the trays alternate to one another and for improving the distribution of liquid and distillation thereof within this concentric portion of the cylindrical baffle section.

The upper end portion of the concentric cylindrical baffle 6 is provided with an annular trough about its periphery formed by L shaped bafile 18 which has drain holes in its horizontal portion. A cylindrical baffie 20 extends downwardly from tray 5 into said annular trough.

A horizontal annular baffle 22 positioned within and near the upper end of the cylindrical baffle acts as a liquid knock-down baflie during operation. That is, as crude oil charge is introduced by N1 or tangential inlet conduit 24 as shown in FIG. 4 to within cylindrical baffle 6, any liquid material tending to climb the wall of baffle 6 is knocked down by baflie 22. Within the conical section 12 there is provided a batfie on which is arranged to channel the flow of liquid downwardly so that it must first flow over upwardly extending weir or bafiie 28 before it flows across the upper tray 16 to its downcomer channel 30. Liquid material discharged from channel 30 onto the next lower tray 16 then flows across the tray to downcomers 32 and 34. Eventually liquid material is collected in an annular collection pot 36 and overflow therefrom into the cylindrical chamber 38 therebelow as a residua product of the charge introduced by N1. Stripping gas such as steam is introduced to the upper portion of chamber 38 beneath lowermost tray 16 by P3 as shown in FIGS. 1 and 2. Conduit 40 is provided for withdrawing liquid residue from the bottom of collection chamber 38.

The annular distillation section of the tower is formed by an annular liquid impervious baffle 42 through which the satellite distillation cartridges 4 downwardly extend. The satellite distillation cartridges are open on each end, with the upper end of each provided with a transverse baffle member 44 provided to direct the flow of liquid onto the upper distillation tray 46 on the end thereof opposite to the tray downcomer 48. Liquid material moves downwardly through each satellite distillation section for eventual discharge into the lower annular chamber 50 in the lower portion of the tower. Withdrawal conduit Q1 or 52 provides for removingresidua from the bottom of the annular section. FIG. 2 shows conduit means P1 and P2 comprising a Y shaped distributor manifold for introducing steam into the annular section beneath the satellite distillation cartridges and lower most tray thereof as shown in FIG. 1. Liquid material such as crude oil is introduced to the annular portion of the tower by N2 or conduit means 54 arranged to provide for tangential inlet at the end thereto as shown in FIG. 3. Beneath inlet means 54 (N2) there is an annular bafiie means 56 provided with vertically extending liquid deflecting baffle section 58 adjacent each cartridge distillation section. Deflecting bafiies 53 are arranged with respect to the open upper end of the satellite distillation cartridges to cause liquid passed into the annular section to flow from annular bafiie 42 over a lip or weir comprising the upper end of the cartridge and thence under a bafile 44 into the cartridge and on a side of the upper most tray thereof away from its downcomer, rather than down through the open upper end of the cartridge. Thus the liquid must traverse the entire width of the tray before passing over the weir comprising the inlet to its downcomer 48. As mentioned above, the tray means employed in the tower above tray 5 and provided for obtaining a plurality of common products of distillation may be either valve trays, sieve trays or even bubble cap trays. Also the tray means employed in the distillation sections of the tower above described may be selected from the above identified various kinds of tray means. In the tower design of this invention it is preferred to use either sieve or valve type tray means except as otherwise specifically specified.

The tower design of the present invention has an overall height between heads of about 104 feet and is about 23 feet in diameter. The concentric cylindrical bafile is about 14 feet, 9 inches in its upper diameter, about 9 feet diameter in the intermediate section and about 12 feet, 6 inches at the bottom. The lube flash section within the concentric baffle is about 16 feet above the uppermost tray or distillation cartridge therebelow. Each distillationcartridge is about 9 feet in overall height.

FIG. 4 shows in cross-section the tangential inlet N1 (24) provided for introducing a hydrocarbon material tangentially within the upper portion of the concentric cylindrical batfle member 6. FIG. 2 shows steam inlet pipes P1 and P2 branching into Y pipe section which discharge steam through a plurality of openings in the upper pipe surface to the lower portion of the satellite distillation cartridges. Steam inlet pipe P3 on the other hand terminates into an open ended T pipe section and discharges beneath the lowermost tray or ring 36 Within the concentric distillation section as discussed above.

The fractionating tower design of this invention and method of operation is advantageous particularly when imposing maximum viscosities and pour point restrictions on crude residuums. Thus the system of this invention provides the method and means for obtaining both low and high sulfur residuums from the crudes charged thus permitting appropriate disproportionating of viscosity and pour point to be made for maximum value of each.

Having thus described the crude fractionating tower of this invention and discussed specific embodiments going to the very essence thereof, it is to be understood that no undue limitations are to be imposed by reason thereof except as defined in the following claims.

We claim:

1. A fractionating tower for separating at least two different crude oil charge materials simultaneously comprising in combination:

a cylindrical distillation chamber separate from a plurality of adjacent separate distillation cartridge means positioned in the lower portion of the tower,

an elongated rectification section above said distillation means and containing a plurality of vertically spaced apart fractionating trays,

each of said distillation means provided with a plurality of vertically spaced apart distillation trays,

the upper end of each of said distillation means being in open communication with the bottom portion of said rectification chamber and separate therefrom by tray means arranged to channel liquid collected thereon into said cartridge distillation means,

feed inlet means to an upper inner flash zone portion of said cylindrical distillation chamber and feed inlet means to an annular section of said tower above said cartridge distillation means,

spaced apart liquid withdrawal and inlet means throughout the vertical height of said rectification section,

and means for withdrawing residual product from the bottom of said cylindrical distillation chamber separately from the bottom of said annular section.

2. A fractionating tower design comprising in combination,

an upper rectification section and a lower distillation section,

a generally cylindrical section of smaller diameter than said tower formed by concentric baffies extending from the lower bottom upwardly through said distillation section, an intermediate cylindrical portion of said generally cylindrical section being of smaller diameter than said end portions, said intermediate portion provided with a plurality of vertically spaced apart horizontally disposed perforated tray member provided with one or more liquid downcomers,

the annular space between said generally cylindrical section and said tower wall provided with a horizontally disposed liquid impervious annular bafile member except as provided below and positioned adjacent the upper edge of said intermediate cylindrical portion,

a plurality of open ended separate distillation cartridges extending through said annular baffie and downwardly therefrom, each of said distillation cartridges provided with a plurality of vertically spaced apart horizontally disposed distillation tray members provided with liquid downcomer means,

means for introducing gasiform material beneath the lowermost tray in each distillation section,

means for introducing hydrocarbon material tangentially to the upper interior portion of said generally cylindrical flash zone section,

means for introducing hydrocarbon material tangentially to the annular section above said annular batlie member,

means for controlling the level of liquid in the bottom portion of said cylindrical and annular sections and for separately withdrawing liquid from each thereof, and

means provided throughout the vertical height of said rectification section for withdrawing common fractions of rectification and return of common products of separation as reflux material.

3. A fractionating tower comprising in combination an upper rectification section and a lower distillation section, said distillation section separated into a smaller diameter concentric cylindrical distillation means surrounded by a plurality of separate satellite distillation cartridge means,

the lowermost tray of said rectification section being adjacent the open upper end of said concentric distillation means and provided with downcomer means for passing liquid therefrom to an annular space housing said satellite distillation cartridge means,

means for separately introducing hydrocarbon material into said concentric distillation means and said annular space,

separate withdrawal means from the bottom of said 8 concentric distillation means and said annular section and means for introducing gasiform material to the lower portion of each of said distillation means.

4. The fractionating tower of claim 3 wherein each of said satellite cartridges means is open at its upper and lower ends and extend downwardly from a liquid impervious bafile member except as provided by said cartridge means.

5. The fractionating tower of claim 3 wherein the central distillation means is provided with upper and lower cylindrical baflle extensions which are of larger diameter than a central distillation section and one of the hydrocarbon charge material to be fractionated is first introduced tangentially to the interior of said cylindrical bafile extension above said central distillation section.

6. The fractionating tower of claim 3 wherein the lowermost tray in said rectification section is a bubble cap tray.

7. The fractionating tower of claim 3 wherein the trays used in the distillation means are either sieve or valve type trays.

8. The fractionating tower of claim 3 wherein a plurality of withdrawal and inlet means are provided throughout the vertical height of said rectification section.

9. The fractionatng tower of claim 3 wherein either sieve trays or valve type trays are employed above the lowermost tray of said rectification section.

10. The fractionating tower of claim 3 wherein the plurality of separate distillation cartridges are equally spaced about said concentric distillation means.

References Cited UNITED STATES PATENTS 3,412,016 11/9168 Graven 202l58 3,544,428 12/1970 Mellbom 202-158 NORMAN YUDKOFF, Primary Examiner D. SANDERS, Assistant Examiner US. Cl. X.R.

233 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION v Patent No. 3,8u6,2h9 e Dated November 197A Inventofls) HORACE B. MERRIMAN It is certified that errar appears in the above-identified patent and that said Letters Patent are hereby corrected as shew-n below:

Column M, (Table 2) line 32 "36o".eheu1d be 630-- Signed and sealed this 7th day of January 1975.

(SZAL) Attest:

I-igCOY M. mason JR. I I c; r'msmuer. DANN Attesting Officer Commissioner of Patents 

1. A FRACTIONATING TOWER FOR SEPARATING AT LEAST TWO DIFFERENT CRUDE OIL CHARGE MATERIALS SIMULTANEOUSLY COMPRISING IN COMBINATION: A CYLINDRICAL DISTILLATION CHAMBER SEPARATE FROM A PLURALITY OF ADJACENT SEPARATE DISTILLATION CARTRIDGE MEANS POSITIONED IN THE LOWER PORTION OF THE TOWER, AN ELONGATED REDTIFICATION SECTION ABOVE SAID DISTALLATION MEANS AND CONTAINING A PLURALITY OF VERTICALLY SPACED APART FRACTIONATING TRAYS, EACH OF SAID DISTILLATION MEANS PROVIDED WITH A PLURALITY OF VERTICALLY SPACED APART DISTILLATION TRAYS, THE UPPER END OF EACH OF SAID DISTILLATION MEANS BEING IN OPEN COMUNICATION WITH THE BOTTOM PORTION OF SAID RECTIFICATION CHAMBER AND SEPARATE THEREFROM BY TRAY MEANS ARRANGED TO CHANNELL LIQUID COLLECTED THEREON INTO SAID CARTRIDGE DISTILLATION MEANS, FEED INLET MEANS TO AN UPPER INNER FLASH ZONE PORTION OF SAID CYLINDRICAL DISTILLATION CHAMBER AND FEED INLET MEANS TO AN ANNULAR SECTION F SAID TOWER ABOVE SAID CARTRIDGE DISTILLATION MEANS, SPACED APART LIQUID WITHDRAWAL AND INLET MEAND THROUGHOUT THE VERTICAL HEIGHT OF SAID RECTIFICATION SECTION, AND MEANS FOR WITHDRAWING RESIDUAL PRODUCT FROM THE BOTTOM OF SAID CYLINDRICAL DISTILLATION CHAMBER SEPARATELY FROM THE BOTTOM OF SAID ANNULAR SECTION. 